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Towards a conceptual framework for explaining variation in nocturnal departure time of songbird migrants

Müller, Florian; Taylor, Philip D.; Sjöberg, Sissel LU ; Muheim, Rachel LU ; Tsvey, Arseny; Mackenzie, Stuart A. and Schmaljohann, Heiko (2016) In Movement Ecology 4(1).
Abstract

Most songbird migrants travel between their breeding areas and wintering grounds by a series of nocturnal flights. The exact nocturnal departure time for these flights varies considerably between individuals even of the same species. Although the basic circannual and circadian rhythms of songbirds, their adaptation to migration, and the factors influencing the birds' day-to-day departure decision are reasonably well studied, we do not understand how birds time their departures within the night. These decisions are crucial, because the nocturnal departure time defines the potential flight duration of the migratory night. The distances covered during the nocturnal migratory flights in the course of migration in turn directly affect the... (More)

Most songbird migrants travel between their breeding areas and wintering grounds by a series of nocturnal flights. The exact nocturnal departure time for these flights varies considerably between individuals even of the same species. Although the basic circannual and circadian rhythms of songbirds, their adaptation to migration, and the factors influencing the birds' day-to-day departure decision are reasonably well studied, we do not understand how birds time their departures within the night. These decisions are crucial, because the nocturnal departure time defines the potential flight duration of the migratory night. The distances covered during the nocturnal migratory flights in the course of migration in turn directly affect the overall speed of migration. To understand the factors influencing the arrival of the birds in the breeding/wintering areas, we need to investigate the mechanisms that control nocturnal departure time. Here, we provide the first conceptual framework for explaining the variation commonly observed in this migratory trait. The basic schedule of nocturnal departure is likely regulated by both the circannual and circadian rhythms of the innate migration program. We postulate that the endogenously controlled schedule of nocturnal departures is modified by intrinsic and extrinsic factors. So far there is only correlative evidence that birds with a high fuel load or a considerable increase in fuel load and significant wind (flow) assistance towards their migratory goal depart early within the night. In contrast, birds migrating with little fuel and under unfavorable wind conditions show high variation in their nocturnal departure time. The latter may contain an unknown proportion of nocturnal movements not directly related to migratory flights. Excluding such movements is crucial to clearly identify the main drivers of the variation in nocturnal departure time. In general we assume that the observed variation in the nocturnal departure time is explained by individually different reactions norms of the innate migration program to both intrinsic and extrinsic factors.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Circannual and circadian rhythms, Departure, Innate migration program, Migration, Night, Songbird, Time
in
Movement Ecology
volume
4
issue
1
publisher
BioMed Central
external identifiers
  • scopus:84992135515
  • wos:000395310600001
ISSN
2051-3933
DOI
10.1186/s40462-016-0089-2
language
English
LU publication?
yes
id
3e78ae59-cb6c-40b7-8914-3ffc0776594a
date added to LUP
2016-11-15 12:45:25
date last changed
2017-09-18 11:30:17
@article{3e78ae59-cb6c-40b7-8914-3ffc0776594a,
  abstract     = {<p>Most songbird migrants travel between their breeding areas and wintering grounds by a series of nocturnal flights. The exact nocturnal departure time for these flights varies considerably between individuals even of the same species. Although the basic circannual and circadian rhythms of songbirds, their adaptation to migration, and the factors influencing the birds' day-to-day departure decision are reasonably well studied, we do not understand how birds time their departures within the night. These decisions are crucial, because the nocturnal departure time defines the potential flight duration of the migratory night. The distances covered during the nocturnal migratory flights in the course of migration in turn directly affect the overall speed of migration. To understand the factors influencing the arrival of the birds in the breeding/wintering areas, we need to investigate the mechanisms that control nocturnal departure time. Here, we provide the first conceptual framework for explaining the variation commonly observed in this migratory trait. The basic schedule of nocturnal departure is likely regulated by both the circannual and circadian rhythms of the innate migration program. We postulate that the endogenously controlled schedule of nocturnal departures is modified by intrinsic and extrinsic factors. So far there is only correlative evidence that birds with a high fuel load or a considerable increase in fuel load and significant wind (flow) assistance towards their migratory goal depart early within the night. In contrast, birds migrating with little fuel and under unfavorable wind conditions show high variation in their nocturnal departure time. The latter may contain an unknown proportion of nocturnal movements not directly related to migratory flights. Excluding such movements is crucial to clearly identify the main drivers of the variation in nocturnal departure time. In general we assume that the observed variation in the nocturnal departure time is explained by individually different reactions norms of the innate migration program to both intrinsic and extrinsic factors.</p>},
  articleno    = {24},
  author       = {Müller, Florian and Taylor, Philip D. and Sjöberg, Sissel and Muheim, Rachel and Tsvey, Arseny and Mackenzie, Stuart A. and Schmaljohann, Heiko},
  issn         = {2051-3933},
  keyword      = {Circannual and circadian rhythms,Departure,Innate migration program,Migration,Night,Songbird,Time},
  language     = {eng},
  month        = {10},
  number       = {1},
  publisher    = {BioMed Central},
  series       = {Movement Ecology},
  title        = {Towards a conceptual framework for explaining variation in nocturnal departure time of songbird migrants},
  url          = {http://dx.doi.org/10.1186/s40462-016-0089-2},
  volume       = {4},
  year         = {2016},
}